Chirpstack Metrics (lorawan)

[FranciscoLozCoding]

This pull request adds support for ChirpStack/lorawan metrics.

Improvements to metric collection:

• Renamed the function get_node_exporter_metrics to get_prometheus_metrics and added a docstring to clarify its purpose.

Addition of ChirpStack metrics:

• Added new ChirpStack Gateway Bridge and Server metrics to the metrics mapping dictionary.
• Introduced add_chirpstack_server_metrics and add_chirpstack_gateway_bridge_metrics functions to collect and publish Prometheus metrics from the ChirpStack server and gateway bridge, respectively.
• Added new command-line arguments to specify the ChirpStack server and gateway bridge metrics URLs.
• Updated the main_runner function to call the new ChirpStack metrics collection functions and handle exceptions.